Numerous designs are already known in practice, wherein for compacting the fiber material (fiber strand) discharged by a drafting system unit, a compaction unit is situated downstream. Following such a compaction unit, the compacted fiber material, after passing through a nip point, is fed to a twist generation device. Such a twist generation device in a ring spinning machine, for example, is composed of a traveler that revolves on a ring, and the yarn produced is wound onto a rotating bobbin. Suctioned revolving, perforated suction drums or revolving aprons provided with perforations are essentially used as compaction units. A specialized suction area on the compaction element is thus defined by using appropriate inserts inside the suction drum or inside the revolving apron. These types of inserts may be provided, for example, with appropriately shaped suction slits to which a negative pressure is applied, thus generating a corresponding air flow at the periphery of the particular compaction element. In particular, protruding fibers are incorporated as a result of this air flow which is oriented essentially transversely with respect to the direction of transport.
In the known approaches, the fiber material delivered by the drafting system unit is guided above or also below the compaction devices. In particular for use on a ring spinning machine, it is necessary to provide an additional nip point downstream from the suction zone in order to get a twist stop.
These types of devices have been illustrated and described in the publications EP 947 614 B1, DE 10 2005 010 903 A1, DE 198 46 268 C2, EP 1 612 309 B1, DE 100 18 480 A1, and CN 1712588 A, for example. These cited publications essentially involve fixedly mounted compaction units that are installed following the particular drafting system. The drive of these compaction units is sometimes achieved via specialized drive shafts that are situated over the length of the spinning machine and are in drive connection with either a suction roller or a revolving apron, or via a fixedly installed drive connection to appropriately situated pressure rollers of the compaction device. Likewise, examples of drives are found in the exemplary embodiments of the cited publications, wherein the drive of the compaction unit is achieved via additional drive elements of the top and bottom rollers of the pair of delivery rollers of the drafting system unit. In practice, it is necessary to retrofit existing spinning machines with a conventional drafting system unit having such a compaction device in order to also ensure the possibility of producing high-quality yarns. Therefore, devices have been proposed by means of which conventional drafting systems may be retrofitted with such a compaction device. One such example is found in DE 102 27 463 C1, for example, in which the punch of the drafting system unit is extended in order to support an additional drive roller provided for the drive of the retrofitted compaction device that is likewise situated on this extension. The drive roller extends over the entire length of the spinning machine. The mounting and installation of such a retrofit unit is very time-consuming and inflexible. That is, a desired dismantling to a standard drafting system without a compaction device is in turn very time-consuming.
A design is known from CN 101613896 A in which an additional element is screwed to the punch for extending the punch of the drafting system. Also described in this exemplary embodiment, is a gearing stage having gear pairs via which the drive of an additional compaction device is to be achieved. This device is also relatively time-consuming for the retrofitted attachment, in particular also due to the additional installation of the disclosed gearing stage.
In addition, a design having a compaction device is disclosed in DE 100 50 089 C2, which is provided for retrofitting of a conventional drafting system unit. A device is proposed that allows the drafting system unit to be retrofitted with a compaction device without additional drive members. Different designs of compaction devices are disclosed in the exemplary embodiments of the cited publication. In all the disclosed devices, a second nip point for the fiber material is formed by the compaction device itself or via drive elements that are connected to the compaction device. The compaction device or drive elements connected thereto rest(s) on the top roller of the pair of delivery rollers of the drafting system unit. That is, in this case no additional nip point is provided on the compaction device, which is formed independently from the rollers of the drafting system unit. Thus, the fiber material delivered from the nip point of the delivery rollers of the drafting system unit does not make contact in the area of the suction zone, which is located in front of the second nip point. That is, most of the fiber material delivered by the drafting system unit moves at a distance from the surface of the compaction device in the area of the suction zone. Thus, controlled compaction or incorporation of protruding fibers is not ensured. Furthermore, the cited publication does not address how the additionally installed compaction device is mounted on the spinning machine or on the drafting system unit.
A device is known from CN 2 851 298 Y in which a compaction roller together with a twist stop roller are accommodated in a bearing element that is connected by means of a plate to a pivotable weighting arm of a drafting system device via screws. In the installed and locked position, the drive is transmitted via friction from a delivery roller connected directly to a drive and its associated pressure roller to the compaction roller and the twist stop roller. The compaction device disclosed here is likewise provided for retrofitting on existing drafting system units of spinning machines without compaction. The mounting of the compaction unit disclosed here on an existing drafting system unit via a screw connection, as well as the threading for the axle of the pressure roller, is relatively time-consuming, and requires additional adjustment of the distances. Likewise, the connection to a negative pressure source must also be established separately. Since the compaction roller is driven only indirectly via friction by a roller directly connected to a drive, drive losses result in this approach.